Looking at glasses with the lens of solid state physics, it turns to be natural to study their low-energy excitations.
In particular, on large scales, glasses are continuum media and thus, at small enough frequencies,
the density of states \(D(\omega )\)  follows Debye's law [1]}, i.e., \(D(\omega ) \sim \omega ^{d-1}\)  in \(d\)  spatial dimensions.
Debye’s law assumes that the only low energy excitations are phonons. Debye's law provides precise theoretical predictions for the thermodynamic
quantities such as the specific heat at low temperatures. However, differently from crystalline solids, glasses show anomalies in thermal
conductivity and specific heat as temperature decreases towards zero [2]}. For instance, the specific heat \(C_v\)  scales with \(T\)  deviating
from Debye's law. Moreover, thermodynamic anomalies are shared by different glassy systems suggesting that universal mechanisms are responsible
for that [2]}.
